1. Field of the Invention
The invention relates generally to cutting devices useful for cutting tubular and structural members, such as those in a subsea environment immersed in fluids or a downhole or subsurface applications involving structural and operational control, formation evaluation and monitoring members. The invention also relates generally to cutters used for cutting core samples and drilling in wellbore walls.
2. Description of the Related Art
Pipe cutters are used to cut tubular members. Pipe cutters typically include a circular cutting blade that is mounted upon a spindle. The spindle, in turn, is mounted upon an arm that can be moved radially out through a slot in a surrounding housing to be brought into cutting contact with a surrounding tubular member to be cut. During cutting, the blade can rotate at approximately 1000 rpm. Pipe cutters are often used downhole, being run in on a tool string to cut a casing member within a wellbore. Commercially available pipe cutters include the MPC Mechanical Pipe Cutter from Baker Hughes Incorporated of Houston, Tex.
In operation, the pipe cutter is disposed within a tubular member to be cut, and the cutting blade is rotated by a motor. The supporting arm is then moved so that the cutting blade is placed in cutting contact with the tubular member. The pipe cutter also rotates about it central axis, causing a circumferential cut to be made in the surrounding tubular member.
Cuttings or filings create a problem during cutting. They can cause damage to the cutting blade or prevent a clean cut from being made. Efficiency of a pipe cutting operation is affected by materials accumulated and packed in the cutting groove. As a cut is made deeper, the cuttings can become trapped within the cut, magnifying associated operational efficiency deterioration and wear and tear problems.
Piping and well structural members used today are made of progressively harder materials, and this makes pipe cutting performance more challenging. During pipe cutting operations, it has been noticed that random and unpredictable torque load fluctuations at times can lock the cutting blade into the pipe, requiring continuous cutting parameters (e.g., torque load, RPM, feed rate, electrical or hydraulic power consumption, cutting efficiency, equipment temperatures, etc.) monitoring and adjustments to reduce the operational frequency of cut interruptions. Cutting adjustments and interruptions lower operational efficiency by increasing cutting time, lower energy cut efficiency and increasing wear and tear in the cutting elements and power drive train. These variations in cutting torque load and cutting advancement rate often requires real time adjustments to the cutting controls due to the equipment's input power constraints available, strength limitations of the cutting elements such as blade or coring bit, cutting edge materials endurance and abrasion wear resistance due to the cutting action, limitations of the power drive providing rotation action such as electrical motor or hydraulic pump, thermal generation and dissipations of the equipment assembly characteristics in the operating temperature, etc. These load and cutting rate variations are amplified and aggravated by cuttings and debris accumulated in the cutting groove during the cutting operation resulting in reduced cutting energy utilization efficiency, reduced cutting productivity (i.e. cutting rate reduction or interruption), increased cutting equipment wear and tear, higher maintenance costs, frequency and effort, increased difficulty and even impediment to cutting thicker pipes with harder specialty alloys for example.
Sidewall coring cutters are used to cut cylindrical coring samples in the wall of a wellbore. These coring cutters are also prone to problems relating to cutting or filings as these tend to prevent a clean cut from being made and/or cause damage to the cutter.